United Kingdom, March 8 -- Amanda Seyfried's son isn't actually called Thomas.

The 39-year-old actress is married to 'The Newsroom' actor Thomas Sadoski, 48, and while her fans around the world have assumed that he shares a first name with his father, she has now revealed that that isn't true.

She told US TV show 'Extra': "Everybody thinks that my son's name is Thomas. Somebody somewhere made up that his name was Thomas and I'm all for it but his name isn't Thomas. Isn't that funny?... I love that he has a secret name!"

The 'Mamma Mia!' star - who also has a seven-year-old daughter known as Nina - is now appearing in the mystery series 'Long Bright River' and plays the mother of a boy coincidentally called Thomas and she could identity...